Process for preparing 5-hydroxy-tryptamine through new intermediates



PROCESS FOR PREPARING S-HYDROXY-TRYPTA- MINE THROUGH NEW INI'ERNIEDIATES Romeo Justoni, Milan, and Ralfaele Pessina, Casatenovo Brianza, Italy; said Pessina assignor to Francesco Vismara Societfi per Azioni, Casatenovo Brianza, Italy No Drawing. Original application Feb. 21, 1956, Ser. No. 566,776. Divided and this application Feb. 18, 1957, Ser. No. 644,705

2 Claims. (Cl. 260-319) This invention relates to a new process for preparing the therapeutically active S-hydroxy-tryptamine having the formula:

HO OHz-C'Ha-NH;

. and to a group of new substances which we have found to be excellent intermediates for the synthesis of the same. This application is a division of our application Serial No. 566,776, filed February 21, 1956, now abandoned.

Various expensive procedures for the synthesis of hydroxy-tryptamine have already been proposed; we have now discovered a new process for the preparation of this compound employing certain novel intermediates which are illustrated below, which is more advantageous than the processes proposed hereto.

Most of the new intermediates used in our new process are indole derivatives which may be represented by the following general formula:

where X is selected from the group consisting of: H, COOH, COOCH COOC H and the like alkyl-ester groups; Y being COOH or COOR (R being a straight or branched alkyl group containing up to 5 carbon atoms); when X is H, Y also being, besides thegroups mentioned above, a member of the class consisting of:

(1110.) X=H b.) X=OH nited States Patent acid, having the formula OH H H 0 H COHPCHPO 2-0 r-C 2-0 0 l CO0H NH-N (iv) and the corresponding di-alkyl esters, formed with straight or branched alkyl groups containing up to 5 carbon atoms. One of the objects of the present in ention is to provide a new process for preparing S-hydroxy-tryptamine.

Another object is to provide the above said new intermediates compounds and methods for the production thereof.

The starting materials are well known cheap substances which may be technically manufactured, by easy and economical procedures, according to methods already de-. scribed in the chemical literature; they are: p.be nzyloXy-. aniline hydrochloride (which is obtained from p.nitrophenol and benzylchloride, by passing through p.nitrophenol benzylether) and 0: carbethoxy-cyclopentanone (which is obtained from the di-ethyl ester of the adipic acid by treatment with sodium).

The initial step of our invention consists in the preparation of the above mentioned a-keto adipic acid p.benzyloxy-phenylhydrazone (IV).

This new compound is readily obtained as follows: p.benzyloxy-aniline hydrochloride is diazotised inan excess of aqueous hydrochloric acid with sodium nitrite and, after addition of sodium acetate, the obtained diazocompound is reacted with a-carbethoxy-cyclopentanone; the precipitated solid product of the coupling having the formula CH CH Cs PC PO 2- is filtered and treated to ebullition with aqueous sodium hydroxide; acidification yields the new a-keto-adipic acid p.benzyloxy-phenylhydrazone of Formula IV (m. pt. 148- 149 C. from dilute ethanol).

By heating in a boiling anhydrous solventse1ected from the class consisting of benzene and its methyl homologues and dioxan-in the presence of a mineral acid the a-keto-adipic acid p.benzyloxy-phenylhydrazone yieldsthe new 5 benzyloxy-indole 2 earboxyl 3 p propionic acid (Formula II above, where X and Y=COOH;

rn. pt. 191-192 C., from dilute alcohol).

In a strictly analogous Way, but by a somewhat diflerent procedure, the same S-benzyloxy-indole-Z- carboxyl-3-flpropionic acid may be obtained through the corresponding dialkyl esters. For this purpose the new dialkyl esters of u-keto-adipic acid p.benzyloxyphenylhydrazone-which are easily obtained by treatment of the a-keto-adipic acid p.benzyloxy-phenylhydrazone with an esterifying agent selected from the class consisting of methylalcoho l, ethylalcohol, and other like alcohol, diazomethane, diazoethane and like diazoaliphatic derivatives containing up to 5 carbon atoms (e.g. the di-methyl ester of the acid of Formula IV; m.pt. 1l4-ll5.5 C., from methanol) are treated to ebullition in the presence of a mineral acid in an anhydrous alcohol containing up to 5 carbon atoms, as well as in another anhydrous solvent selected from the above mentioned class consisting of benzene and its methyl homologues and dioxan, yielding the corresponding indole derivatives: e.g. the di-methyl S-benzyloxy-indole 2 carboxy-3 -fi-propionate (Formula II, where X and Y=--C0OCH Z=CH C H I freeljfi -lliydroxyl group. 7

' m.pt. 122423.? (3., from. ethanol), the analogous diethyl ester (Formula II, where X and Y=-COOC H Z=.CH -C H m.pt. 108-109 C., from ethanol) and i ha ke- We Q Q at st r a f h gr m ladipic acid p.benzyloxy-phenylhyldraz one and conversion into the corresponding indole'derivative may be also carried out in continuation in the same alcoholic solvent inv presence of a mineralacid-without isolating the inter.- mediate ester of the acid ofrFormula 1V. Alkaline hydrolysis of the said indole di-esters" (Formula II, where r X and Y are carboxy alkyl groups and Z is benzyl group) w o ben lcxrin Q Q-Z- rb xy-3-fi-pmp on acid. 2

edema-agenda convert the 5-benzyloxy group into a i In practicing these steps of our invention,- 5-benzyl oxyindole-l -carboxyl e' 3-propionic acid is' heated preferably at ISO-230 C. alone or in solution and/or suspension an inert high-,boilingliquid,selected from the class con- .sisting of tetrahydronaphthalene, decahydronaphathalene and neutral petroleum derivatives having a-boiling point above 190.. such as parafiin oil; mono-decarboxylation of the dicarboxylic' acid occurs and S-benzyloxyindole-iifi-propionic .acid (Formula H, where Y=COOH, X-I= H' and ;Z --C H -C H5; m.pt. l63-l65 C., from dilute ethanol) is obtained. I

This-indole mono .-carboxylic acid is esterified with a low molecular-alcohol in 'order to obtain'a corresponding new ester: forexample the methyl-ester (Formula II, where Y=1COOCH X=H and1Z =T-CH -C H m.pt. 98-401? 0., r from methanol), the ethyl ester (Formula II, where, Y=COOC H 'X==H and Z=CH C H ;-.m.pt. 62-63 C., from hexane) and ns le d a b xyl ci i ihen'fi nsfcr edby therrnic decarboxylation into a; benzyloxy-indole mono a b l a ds ormul a o e; wh r 'Y=.. 0.0

an Z?.. H2:T 6 s)W 91 rb de theS ,benzyloxy group, contains in the indole nucleus, only a QHEQHPQQ H s d -c i :i 3-P9 t 9n-:i "Ih sn w 9!!. ,P 14 l2 i1t dt e ba s ;t an rm tion [through a series: of; intermediatesiin order toconyert he f exr q -s er ai into 7 the transitorily formed isocyanate, by reaction with the alcohol employed, yields an urethane [Formula H, where X being H and Z=CH C H Y is a member of the class consisting of NHCOOCH NHCOOC H mal and isomers), NH-CO OC5H i (normal andgisomer's') NH- -COOCH C Hgl Tlie'con'stitution of j urethanes also clearly illustrated by the following" genether similar esters, with alkyl groups containing, up'to 5 carbon. atoms:

By boiling with an alcoholic hydrazine hydrate solirtion theso obtained ester is then converted into the corresponding hydrazide (Formula II, Where r By treating the said hydrazidewith sodium nitrite and dilute ethanol) an acid 'in presence of water and of a solvent, selected from the group consisting-ofi'ether, benzene and its methyl homologuesand aliphatic alcohols containing 4. or 5 carbon atoms, thehithertounknown a'z'ide (Formula readily obtained.

As we have verified this azideby 'pyrolysis at 140. I i

C.,' in an inert solvent, and subsequent mild hydrolysis of thesoformed isocyanate (Formula II, where Y='NCO,.

acidm'ay be directly transformed into S-benzyloxytryptamine which, in its turn, may be converted into 5- l iydroxy-tryptamine; However we point out that this way of transforming the above azide into S-hydroxy- V tryptamine furnishes only a very poor yield.

fQlOn the contrary we have discovered that it is possible in' the practice of our invention to convert in a high yield thesaid azide into S-hydroxytryptamine by a better indirect procedure through certain further intermediate compounds'., The conversion is carried out as follows. The a zide, is heated at 60-140 C. with an alcohol selected from the class consisting of methyl alcohol, ethyl alcoliolaother low molecular alcoholscontaining up to 5 carbon atoms and benzyl alcohol. Pyrolysis occurs and eral. formula:

, g H I r V (V) i a where A=alkylor aralkyl group, according to the alcohol employed in its preparation. For example employing methanolthe methyl-urethane ie. the B-[3-(5-benzyldxy' ndo1 11?ah 1lc ram c acid methyl ester Formula NH--COOC H (normal and iso), NHCOOC H ,(nor- Y mixing with a small quantity of hexane) is obtained. Similarly ethanol yields the ethyl urethane (Formula with hexane); isoamyl alcohol yields the correspondin isoamylurethane (Formula V, where A=-cn,-oH=-crr-om non crystalline pale yellow glass); benzyl alcohol yields" the benzyl urethane (Formula V, where i i 1 m v m.pt. 72-73 C. irom'vbenzene with hexane).

' The urethane is then subjected to a mild catalytic hydrogenolysisin the presence of a palladium'catalyst in an alcohol solution; by removal of the benzyl group from the S-benzyloxy function the corresponding,non-.ben-

zylated urethane having a, free S-hydroxylgroup ;is V

formed (Formula II, where X and Z= 'H; Y,isa member of the class consisting of: NH-COOCH3LNH'COOC'2H5, j

NI-I-COOC H (normal and iso)"NH-,COOC H (normal and isomers), NH-COOC H (normal and isomers), NH-COOCH -C H hydrolysis of the latter, in an alco:

hol solution, employing as hydrolysing agent a mineral acid in the presence of water, gives, by splitting oil the carbamic ester group, the desired S-hydroxy-tryptamine (Formula I) which is isolated in the form 'of its picrate, or.oxalates, or of its well known double salt: S-hydroxy- .t'rypta'mine-creatinine sulfate.

Particularly when the benzyl-urethane derivative (Formula V, where A,=-CH -C H or Formula-II where Y=NI-I-COO-CH C H X' =H and, Z="-CH -C H is prepared as interm'ediateythe catalytic hydrogenolysis thereof in the presence of an aqueous alcohol and a mineral acid, furnishes directly a very high yieldof S-hydroxy-tryptamin'e; ;Again we have found "that the conversion of any in: termediate -5-benzyloxy-urethane (Formula V) into 5 -hydroxy-trytamine aybe obtainedby carrying out, the same reactions hydrogenolysis and hydrolysis in Example vI (a) g. of p.amino-'phenol-be nzyl ether hydro-' chloride in cc. of water: and 76 cc. of concentrated hydrochloric acid are diazotised with 32.3 g. of sodium 7 nitrite dissolved in 100 cc. of water. 120 g. of sodium acetate are added and then, with continuous agitation at C. the solution is coupled with 66.5 g. of a-carhethoxy-cyclopentanone. Agitation is continued for three hours allowing the temperature to rise to 20 C. The formed solid product is filtered, washed with water, mixed with 1200 cc. of a sodium hydroxide solution and heated on steam bath for three hours. The warm solution is neutralised to pH 7.5 with dilute hydrochloric acid and filtered with charcoal; after cooling the oz-keto-adipic acid p.benzyloxy-phenyl-hydrazone is precipitated with hydrochloric acid; the yield of the filtered, washed and dried product is 128 g.: yellow crystalline powder m.pt. 146-148 C. (A sample recrystallised from 50% ethanol shows m.pt. 148149C.; the determination of N content is in agreement with the formula C19H2005N2: calc. found 7.98.)

(b) A solution of 125 g. of the above a-keto-adipic acid pbenzyloxy-pheny'lhydrazone in 1250 cc. of dioxan containing 5% of dry hydrogen chloride is refluxed over a period of twenty minutes. After cooling the formed ammonium chloridegis filtered by suction and washed with a little of dioxan. The clear filtrate is adjusted to pH 8 by adding a 10% aqueous sodium carbonate solution'. The solvent is then distilled at 30 mm. pressure so obtaining about 300-400 cc. of a concentrated residual solution which, after neutralisation to pH about 7.2, is decolorised With charcoal and filtered. The filtrate is made acid to Congo red with hydrochloric acid thus precipitating the crude S-benzyloxy-indole-Z-carboxyl-3-fi-propionic acid which is collected on a Biichner funnel, washed with water until the washings are neutral to litmus and dried on steam bath. The yield of the crude product melting at about l71-173 C. is.

103 g. After repeated crystallisations from aqueous ethanol (1:1) 80 g. of pure, white S-benzyloxy-indole-Z- carboxyl-3-fi-propionic acid melting at 188190 C. are obtained. (An analytical sample shows m.pt. 191-192 C.; determination of N content gives values according to the formula C H O N: N% calc. 4.12; N% found 4.06.)

This step (b) may be carried out also employing instead of dioxan the benzene or toluene as'solvent for the indole cyclisation. In this case however the yields are lower.

(0) Four 20 g. portions of S-benzyloxy-indole-Z-carboxyl-3-fi-propionic acid, suspended in four 200 cc. portions of paraffin oil, are heated at ca. 210 C. in an oil bath; melting and decarboxylation occurs. The heating is continued for one and half hours. After cooling at ca. 60 C. the mixture is extracted with 300 cc. of aqueous 10% sodium carbonate solution: the pH of the obtained brown solution is then adjusted to about 7.2 and the solution filtered with charcoal from separated tar. By acidification with dilute hydrochloric acid, 62 g. of crude 5-benzyloxy-indole-3-/3-propionic acid, melting at 150- 151 C. with sintering at 118 C. separates ofi. This product recrystallised from the minimal amount of 50% aqueous ethanol melts at 153156 C.; yield 42.8 g. (61% of the theoretical amount). (An analytical sample twice recrystallised from 50% ethanol melts at 163-165 C. and the nitrogen determination is in good agreement )formula C H O N: N% calc. 4.74; N% found (d) A solution of 42 g. of the above S-benzyloxyindole-3-B-propionic acid in 420 cc. of absolute methanol, containing 3% of dry hydrogen chloride, is refluxed for a period of two hours. After cooling, the mixture is poured into a solution of 43 g. of sodium bicarbonate in 900 cc. of water. The separated crystalline brownish solid is collected on a filter and washed with water giving 43.3 g. of methyl-5-benzyloxy-indole-3-fl-propionate: M.pt. 98-99 C. (An analytical sample recrystallised from methanol shows m.pt. 100-101 C. for C H O N: N% calc. 4.53; N% found 4.37.)

(e) A mixture of 43 g. of the above methyl-S-ben zyloxy-indole-3-}8-propionate, 1160 cc. of ethanol and 63 cc. of hydrazine hydrate is heated under reflux for one hour. After removal under reduced pressure of most of the solvent, the residual solution is diluted with an equal volume of water, and the precipitated crystalline solid is filtered andwashed with water. The m.pt. of the crude hydrazide is 133135 C. After crystallisation from 70% ethanol, pure 5-benzyloxy-indole-3 5-propionhydrazide is obtained in an amount of 40.8 g. (96% of the theoretical amount): M.pt. 134-136 .C. (An analytical sample, recrystallised from Water, melts at 137- 138 C.: for C H O N N% calc. 13.59, N% found 13.70.)

(1) To a solution of 40 g. of the above hydrazide in cc. of acetic acid, 510 cc. of water chilled to 0 C. and 330 cc. of benzene are added with stirring. The resulting mixture is then treated with 100 cc. of a 10% aqueous-sodium nitrite solution, stirring being continued for five minutes more. After separating the-benzene layer, the aqueous phase is extracted twice with 330 cc. portions of benzene. The to 0 C. cooled combined benzene extracts, are washed firstly with a cooled dilute sodium bicarbonate aqueous solution and then with cooled water until neutral and dried over finely powdered anhydrous sodium sulfate. 7 (A sample-15 cc.--of the filtered benzene solution, evaporated to dryness under reduced pressure at room temperature, gives a yellow crystalline residue of crude 5-benzyloxy-indole-3-fi-propionazide which begins to decompose at 45 C.)

(g) The above benzene solution is added dropwise to 3300 cc. of boiling anhydrous methanol. Continuous distillation of the azeotropic mixture of methanol and benzene occurs.

When all the benzene had been added and distilled, the

' residual methanol solution is refluxed for one hour and then evaporated under reduced pressure to dryness thus obtaining a brownish oil. A concentrated benzene solution of this oil is poured over 70 g. of aluminum oxide and the formed ,B-[3-(5-benzyloxy)-indolyll-ethyl carbamic acid methyl ester is completely eluated by washing the aluminium oxide with benzene. Evaporation of henzene solution at reduced pressure to a small volume (about cc.) and dilution with 15 cc. of hexane gives 27 g. of the methylurethane as white needles m.pt. 9093 C. The mother liquors are again treated with aluminium oxide so obtaining a further amount of the same product. Total yield 31.5 g. (An analytical sample twice recrystallised from benzenehexane melts at 94-95 C.: the nitrogen content is in good agreement with 1h$2f)ormu1a C H O N N% calc. 8.64, N% found (h) A solution of 31 g. of the above methylurethane in 1000 cc. of methanol is treated with hydrogen with continuous stirring at five atm. pressure (room temperature: about 25 C.) in presence of 15 g. of a 10% palladium on carbon catalyst until no more hydrogen was adsorbed (about five hours). The filtered methanolic solution contains fl-[3-(5-hydroxy)-indoly1]-ethyl carbamic acid methyl ester. It was then evaporated unde reduced pressure to a volume of about 400 cc.

(That the debenzylation is accomplished is proved by the fact that a sample of this solution treated in an alkaline medium with an aqueous solution of diazotised sulphanilic acid gives a red colour so confirming the presence of a substance having a free phenolic group.)

The crude methanolic solution containing the B- [-3-(5- hydroxy) -indolyl]'-ethyl carbamic acid methylester is refluxed with 150 cc. of dilute hydrochloric acid (1:1) for 30 minutes to hydrolyse the carbamic ester. The greenish solution, after addition of 9 g. of crystallised sodium acetate, is neutralised to Congo red with sodium bicarbonate and filtered from the separated sodium chloride.

(1') 20.8 g. of picric acid are added to the filtrate, and most of the alcohol is evaporated under reduced pressure.

. "7 'ifheresidualorange-red mixture is diluted to about 400 cc. with'wateii warmed to 50 -6S C; and filtered with charcoal: by cooling 5-hydroxy-tryptamii1e 'picrate separates oti as'red needles mipt. 185-187 C. with eg; after concentration ofthe mother liquors under reduced 7 pressure atm theramount-of thesame picrate is obtained. 7 (A sample jrecrystallised from'water'melts at 196-197 I C. and a mixed melting pointwith an authentic sample of S-hydrQxy-tIyptamine picrategi ves nodepression.)

W -nqapl z' v (a) ci-Keitofadipic'acid p.benzyloxyphenylhydrazone prepared as described in the step (a) of Example 1'.

(b) 128 g. ofthis product are esteriiied employing an excess of adiazomethane methylene-chloride solution; eliminationof-"the-solvent- 'and ofdiazoni'e'thaneexcess" gives '135 grofthedirnethyl-es'ter in form of yellow crystals: 7 An analytical sample recrystallized from methanol shows m.pt'. 114f115.5 C.--and the determination of-N content is inlagreein'ent 'withthe constitution of dim'ethyloz keto adipate --p.benzylo"xy phenylhydraz'one (for 134- g. of thej-above :cr'ude dimethyl-ester are" suspended iu'l660 of absolute methanol containing 10% of dry-hydrogen chloride and refluxed-for twenty minutes. After coo n he reaction mixture-is gradually poured into'a cooled solution of 400g. of sodium bicarbonate-in'-6000cc.- of water. "The separated solid brown product is filtered; washed with water and crystallised from-ethanol so: obtaining 96.5 g. of white crystals; in. pt. -120-121 C.,of dimethyl-5 henzyloxyindolef2-carboxy-3-;8-propionate. if g dryness at re- The mother liquors are evaporated to duced pressure; thedried residue is again taken up with l 350 cc. of absolute -methanol containing 10%, of dry pionate, 111. pt. 120-121" C.

In sucha way the yield arisesto 113 g. (89% ofthe theoretical amount). An analytical sample twice re crystallised from ethanol melts at'122-123.5 C.; the analytical values for N are-in agreement with the formula C H O N N%' calc. 3. N% re nant This di-methyl-ester' is-hydrolysedto the corresponding S-benzyloxy-indole-Z-carboxyl-3 S-pIopioDic acid as follows: to a solution of 112g. of di-methyl-5;benzyl oxyindole 2 carboxyl 3 B propionate in 2250 cc. of ethanol at 40 'C., 985g. of sodium hydroxide dissolved in 164 cc. of Water are gradually added with stirring.

Themixture is then allowed to stand during 12 hours,

at room-temperature (abont 25 C.). -After cooling at C. the sodium salt, which separates 03, is filtered on a Biiclmer funnel, washed with ethanol and-dissolved in" vthe'strictly necessary quantity, of'wat'er. 1 The aqueous solution "decolorised with charcoal is acidified with dilute hydrochloric Tacid and theprecipitat'ed indoledicarboxylic acid is collected; on a Biichner' -funnel,

washed thoroughly with' water and -dried: yield -95 g.

retical' amount); p 7 I I V 'T(c) :Five19 g. portions of -ben'zyloxy indole-2-carboxyl-3i-B-propionic acid are iheated at 215-225 C. in anioiltbathj melting and. decarhokylation occurs. The heatingis continued for one hour. .Aftencoolin ggall. the

obtained ibrownishlsolids are .takenxnp with. warm 70% aqueous .ethanolmandihe solution filteredzwith. .charcoal.

Di ution hu'th Lwatet bring the alcohol Ito. .50.% and cooling causes the separation of 73 g. of crude 5.-henzyl-.

oxy-indole-3-fl-propionic acid. This product recrystah lised from the minimal amount of 50% aqueous eth-.

anol melts at 153-156 C.; yield 49.5 g; (d) (e) (f) (g) This 5-.benz'yloxy-indole-3 fi-propionic acid (49 g.) is converted into fi-[3-(5.-benzyloxy) indolylJ-ethyl'carbahaic acid methyl-ester. (37 'g.') by passing through the steps (d), (e), (f) and (g) of Example 1.

(h) The handling of this step for transforming the said methylurethane into 5-hydroxy-t'ryptamine is l-inverted respect to corresponding step as described in Ex? ample 1: the procedure is as follows: firsthydrolysis' V is carried out bytreating a solution of 37 g. of the meth' yiuretha'ne-in 520 cc. of ethanol with 220 cc. of 6N hydrochloric acid overnight at 40-50 C 2: hydrolysis of the carbamic ester group occurs. To the-fsoiobtained solution containing 5-benzyloxy-tryptamine hydrochloride. 97.8 g; ofsodium bicarbonate are added to'neutralise the excess of hydrochloric acid. After, filtration' of the separated sodium chloride, g. of sodium.

salicylate are added with stirring and the ethanol is evaporated under reduced pressure up to a residual-volume of about 250 cc. By cooling crystallisation occurs;

.,t he collected S-benZyIOXy-tryptamine salicylate, washed.

with alittle water and dried,- forms yellow crystalline needlesmelting at'l67-169 C.; yield 18.5 g. (A water recrystallised analytical sample in fo'rmof white needles shows 111. pt. 174-175 C.: the nitrogen determination is in good agreement with Vformula 17 1s 2- 7 s a V 1 A solntionof 18 g. of the above 5-benzyloxy-tryptamine salicylate in 540cc. of ethanol .is' t reate'd with drogen at five atm. pressure with continuous stirring (room temperature: about 25 6 C.) in presence offl 'g.

of 10% palladium on carbon catalyst until no more f hydrogen is adsorbed.

(i) From the-filtered alcoholic solution containing S-hydroxy-tryptamine salicylate, the indole base is separated as picrate by adding 10.3 g. of picric acid as already is described at the step (i) of Example 1. By

evaporating the orange-red solution to a small volume crystallisation begins. The filtered S-hydroxy-ttyptamine picrate'is washed with ether to eliminate any trace of salicylic acid and recrystallised from water; it is so suspended in 25 cc. of N hydrochloric acid. ;This-s'uspension is long pounded with a rod of glass and repeatedly extracted with ether so as to eliminate picric acid; in this way a limpid aqueous solution ot' '5-hydroxytryptamine hydrochloride is obtained. The ethereal solution is then Washed with 10 cc. of N hydrochloric acid. The clear aqueous solution (cc. 35) is at first neutralised to-Congo red with sodium bicarbonate and then adjusted to pH 7.8-7.9 by addition of sodium carbonate The liquor is extracted repeatedly with h utanol, washing butanolic extracts with a sodium chloridesolution'adiusted to pH 7.9 with potassium carbonate. To the hutanolic solution, previously dried over sodium sulljate,

pressure. The residue is'taken-up with a 'small warm absolute ethanol and-the alcoholic solution filtered with charcoal; by cooling'and addition of'dry etherthefS- hydroxy-tryptamine hydrogen oxalate separates 011 as pale bufi microc'rystals; A further-recrystallisation from V obtained in form of red needles melting at 196-197" also Example 3 (a) By the same procedure as. described in the step (a) of Example 1 a-keto-adipic acid p.benzyloxy-phenylhydrazone is prepared.

(b) 125 g. of this compound is suspended in 500 cc. of anhydrous ether and treated with an excess of a diazoethane methylene chloride solution (prepared in its turn by treating 300 g. of crude moistened 80% nitroso ethylurea-obtained from propionamide according to the method of A. W. Hofmann, Br. 15, 754, 1882, and Werner, Soc. 115, 1100, l9l9-with a concentrated aqueous potassium hydroxide solution in the presence of 3500 cc. of methylene chloride, analogously to what is described in Helv. Chim. Acta 24, 1474, 1941, with reference to the like nitroso methylurea and diazomethane). After 24 hours the excess of diazoethane is destroyed by shaking with dilute hydrochloric acid, and the methylene chloride is evaporated. The crude viscous diethyl-ester is dissolved in 3000 cc. of benzene; 1000 cc. ofthe solvent are distilled to eliminate azeotropically any moisture and into the boiling solutiondry hydrogen chloride is bubbled over a period of one hour. The cooled reaction. mixture is poured into an excess of an aqueous 5% sodium bicarbonate solution and the separated benzene layer is concentrated to a residualvolume of about 300 cc. This residue is adsorbed on 2500 g. of aluminium oxide. benzene (1:1) gives fractions, which after crystallisation from ethanol shows in. pt. l08109 C.; the determination of. the nitrogen content is in agreement with the constitution of diethyl-5-benzyloxy-indole-2-carboxy-3 8- propionate (for C H O N:N% calc. 3.54; N% found 3.70). The same procedureis followed using toluene and xylene (o, m, p mixture) as solvent for the indole cyclisation. The same diethyl-ester is obtained This diethyl ester is hydrolysed in analogous way as described in the step (b) of Example 2 for the corresponding di-methyl ester.

(d), (e), (f), (g) The so obtained 5-benzyloxyindole-2-carboxy-3-B-propionic acid is then converted in B-[3-(5-benzyloxy)-indolyl] -ethy1 'carbamic acid methyl ester according to procedure already described at the steps (f) and of Example (h) A 20 g. portion of the so obtained fi-[ 3-(5-benzy oxy) -indolyl] -ethyl carbamic acid methyl ester is hydrolysed in a perfectly analogous wayas described in the step (h) of Example 2. To the neutralised hydroethanolic solution filtered from sodium chloride, 9 g. of sodium benzoate are added. By concentration under reduced pressure, S-benzyloxy-tryptamine benzoate as yellow needles, m. pt. 148-149" C. is obtained. (An analytical sample twice recrystallised from water melts at 153l54 C. and the nitrogen content determination is in good agreement with the formula C H ON .C- H O or C H O N N% calc. 7.22, N% found 7.40.)

Analogously as in Example 2 at the end of the step (h) an alcoholic solution of 9 g. 5-benzlyoxy-tryptamine benzoate is treated with hydrogen in presence of 10% palladium on carbon catalyst.

(1') By addition of picric acid (5.15 g.) and concentration of the orange-red solution, the S-hydroxy-tryptamine picrate is separated by handling as described at the end of the step (i) of Example 2.

(I) If desired, from the 5.-hydroxytryptamine picrate may be prepared the S-hydroxy-tryptamine oxalate, according to the directions described in Example 2 at step (I) for the corresponding hydrogen oxalate, with the sole difference that the oxalic acid is employed in calculated amount for obtaining the neutrum oxalate. The 5-hydroxy-tryptamine oxalate melts at 193'-195 (dec.) after one crystallisation from ethanol. (Analysis i13 ;r9C)3 H ON C H O N% calc. 12.7; N% found Elution with hexane and hexane Example 4 (a) a-Keto-adipic acid p.benzyloxy-phenyl-hydrazone is prepared as described in the step (a) of Example 1. I (b) g. of this dried product are at once treated with 1500 cc. of absolute ethanol containing 10% of dry hydrogen chloride and the mixture allowed to stand at room temperature for 24 hours is then refluxed for twenty minutes. The transitorily formeddiethyl-ester is so didimethyl-S-benzyloxy-indole-2-carboxyl-3-fi-propionate is obtained. This product recrystallised from ethanol melts at 120-121 and is identical'to the dimethyl-ester obtained as said in the step (b) of Example 2.

The indole dicarboxylic ester (methyl or ethyl) is hydrolysed as described at step (b) of Example 2 to the corresponding 5 benzyloxy-indole-2-carboxyl-3-fl-propionic acid. g

(c), (d), (e) 80 g. of this indole dicarboxylic'acid are then converted into 5-benzyloxy-indole-3-;3-propionhydrazide by passing through the steps (c), (d) and (e) of Example 1.

(f) The 5-benzyloxy-indole-3 p propionhydrazide so obtained (40 g.) is converted into the corresponding azide as reported in the step (f) of Example 1, with the sole difference that ether is employed in place of benzene.

'(g) The ethereal solution of azide, about 650 cc. dried over powdered anhydrous sodium sulfate is added dropwise to 1300 cc. of boiling anhydrous ethanol in such a rate that ether distills off.

When all the etheral solution has been added and distilled, the residual ethanolic solution is refluxed for one hour and then evaporated to dryness under reduced pressure thus obtaining a brownish oil. A concentrated benzene solution of this oil is poured over 65 g. of aluminium oxide and the }3[3-(5-benzyloxy)-indo1yllethyl carbamic acid ethyl ester is completely eluted by washing the aluminium oxide with benzene.

Evaporation of benzene solution to a small volume (about cc.) and dilution with 13 cc. of hexane gives about 28 g. of the said ethyl urethane. The mother liquors were again treated with aluminium oxide so obtaining a further amount of the same product. Total yield 32.2 g.: 111. pt. 86-87 C. (An analytical sample twice recrystallised from benzene hexane melts at 87- 88 C. The nitrogen determination is according to the formula C H O N :N% calc. 8.28, N% found 8.05.)

(h) A solution of 30 g. of the above ethylurethane in 1050 cc. of ethanol is treated with hydrogen with continuous stirring at five atm. pressure (room temperature: about 25 C.) in the presence of 10% palladium carbon catalyst until no more hydrogen is adsorbed (about five hours). The filtered solution, which contains fi-[3-(5- hydroxy)-indolyl]-ethyl carbamic acid ethyl ester, is then evaporated under a reduced pressure to a volume of about 450 cc.

The crude solution of the so formed non-benzylated ethylurethane is refluxed with cc. of dilute hydrochloric acid (111) for 30 minutes to hydrolyse the carbamic ester group. The green solution, after addition of 9 g. of crystallised sodium acetate, is neutralised to Congo red with sodium bicarbonate and filtered from the separated sodium chloride.

(i) 20.2. g. of picric acid-are added to the filtrate,

" tallised sample melts $2 3- TC; i 7

7 ;1 1 and most of the alcohol is ev aporated under reduced pressure; The residual orange-red mixture is diluted to abput450 cc. water, warmed to 60 6? and filtered" with I charcoal; "by coolingv hydroxyt'ryptmin'e picr'ate separates ofi as red needles,"m.;pt. 185 187 CLwith reduced pressurefa further amount ofthe'samepicrate V converted in 5 -hydroxy-tryptamine hydrochloride as de scribedrat'stepfl) of Examplej2. To. the iobtained aque-i ous' solution, neutralised to congo-rediwith 'sodium"bi carbonate,.2.7 'g. of creati'nine,f42O 'cc. ofethanol; 23.5 CC'rQf; 2- N sulfuric acid'are addedn The-resultingsuspension is; heated tohboilingpand then cooled at 0'1 C.

' -hy y-t 'yptamine creatinine sulfate separates'otf' asa' white;crystalline precipitate. .The product is filteredon huer1f nne1. Wa e with alcohol and dried. Yield? ,1jE mP f f. th-KetE-adiflc a d'1 -"be y q y-phefiy r y r ouc; is'preparedas described in the step '(a') of Example 1.

(5) 128 g. of this product are refluxed for'twenty minutes with 1 500 cc. ota 10% solution of dry hydro gen chlorideirpsiec; butyl carbinol (activeamyl-alcoholf rrernienmnmi {{Ihe cooled reaction mixture, washed:

firstly'with an excess: of 5% aqueous sodium .bicarbonatefi; solution andth'en with water until neutral, is dried and evaporated to dryness under reduced pressure. I "(flhrorna-F tography of aluminium oxide of a concentrated benzene; solutionlof the residue, gives, by elutionwith hexane-andhexaiie-benzene (121), the di-Z-methylbutyl-S-benzyloxyindole-2-carb'o'xy-3 fl-propionate in the fornrpf-a viscous colourless oil. v.Saponificationof this ester with'fa wargmw alcoholie'solution of sodium hydroxidegives90 g. of 5--fbenzyloxy-indole-2-carboxyl-3 -,6-propionic acid; 7 (c)- This .indole. dicarboXyIicacid'QO g.) is refluxed-1 with 720' cc. of boiling tetrahydronaphthalene forfseven hours, until theevolution .of.carbondioxide has ceased; After cooling, theseparated crystallineproduct-is filtered and .drled z. 66- .g. if: '5ebeniyloxy-indole 3 -fl-propionicf j acid, melting at 153-157f. C., are obtained Qoncen tration of the .mother liquors: under reduced pressuregives a second crop of 6.4 g. melting at 151-155 C. Thetotal yield of S-benzyloxy-indole 3-fi-propionic 'acid1 O amounts in this way to about 92% of the theoretical amount; the product is satisfactory for the next stepx- (A mixed melting point of a sample recrystallised from aqueous ethanol with a' pure sample of the indole mono-' carboxylic acid gives no depression.) Byextraction of the residual-mother liquor with a dilute aqueous'sodiunr bicarbonate solution and following acidification thereof, 5.5 g. of'a; mixture of monoand not changed bi-carboxylic acid melting at .171-1'/'6 C. are obtained; This third crop may be recycled so .giving a further small amount,

. of 5-benzyloxy indole-3-B-propionic acid.

The same procedure has'been experienced using deca hydronaphthalene j as, solvent for the. decarboxylation; a similarly good yield'ofthe same indole-mono-carbox ylic acidisobtained. a ('d) A solution of 72 g. of 5-benzyloxy-indole-3-BQ propionic acid in -720 cc. ,of isoamyl alcoholcontaining 3% ,olfdry hydrogen chlorideisrefiuxeld overaperiod.

of twoi hours. AiterLc QIin'gQtheniiXtiIre "is first washed with] n. exse gq ya .dilt eaqu eu d mgbiicja'rbonate solution, and themwi tli wateruntil'neutral thus obtaining anv i y 9 1 i1 fi9n got. i Qai y1-i uiv1o y-in dole-i 'fi-propionate.

(To recognise the. presence offt statesmen;-

spars-er a .(f) To the above isoamyl alcohol solution a 12 and then evaporated to drynessin vacuo. 'A concentrated benzene solution of the residual brownish 'oil is chromatographed on 50 gIof aluminiumIoxide; After 1 a complete 'elution with hexane, benzene and amixture: consisting ofequal volumes of benzene and ether fol-- lowed by evaporation of eluates under reduced pressure the isoamyl ester is obtained as'apale yellow'glassz. 3.2, g. The latter isdissolved in 70 cc. of ethanol at 40f C. and hydrolysed by adding a solution'of 2.8; g. of hydroxide in 7 cc. of water. After standing at room 7 temperature (about 25 C.) during 24 hours, the mixture is cooled to 0 C. and the separated sodium salt, filtered I on a B iichnei' funnel and washed with. ethanol;

aqueous concentrated solution of the sodium saltpisjf acidified withv dilute hydrochloric acid and the precipie tate filtered, washed thoroughly with-water and-: I The product-about 2.1 g. of white crystals melting at 161.162 C. is recognised as 5-benzyloxy-indole-3 B- *sa'mple.) (e) The. above isoamyl alcohol solutioncont'aining the main fraction of isoamylfes'ter is refluxed with cc. of hydrazine hydrate for one hour... After the solution containing the 5- ben zyloxy-iridole-3fil-isroi pionhydrazide is transferred to a, separating. repeatedly" washed with water. and, i finally, "semeste containing a little hydrochloric acid to eliminatethe'ex? cess of hydrazine. (A 35 cc. sample of the ispainyI-alcohol solution after evaporation in vacuqg'iys a crystalline residue which, after crystallisation from di lute ethanol; melts at -136 C. and'gives nc i' depl'esif sion when mixediwith an authentic sampleof 5-benz'yl; oxy-indole-3-B propionhydrazide.)

drazide a solutionof 18 g. of sodium nitrite in' 180 cc; ofwater is added. After cooling toO C. and 22.2 cc. of concentrated hydrochloric acid diluted with 50 cc; of water are dropped inthe mixturef Afterstaiid-l;

ing for five minutes the isoamyl alcohol layer 'is' s parated" and the aqueous phase extracted witli350 ccnof fisoamyl alcohol. The combined extracts, washed 'fir's'tly "a" dilute aqueousj'sodium bicarbonate solution and then with water until neutral, aredried over anhydrous potassium. carbonate. i 1 I (g) The filtered isoamyl alcohol solution, containing the 5-benzyloxy-indole-3-,8- propionazide, is refluxed for. one hour in a round-bottomed flask, employing anapp ratus equippedin such'a way'that the isoaniyl ,alc'oh 'f' refluxing in thefiask was dried by contact with phe phoric anhydride. Formationof'the isoamyl'uretha '1 occurs. (A 35.cc.. sample of the obtained' solut ionf. evaporated to dryness under reduced pressure. A eon-, centrated benzene solution of the residual brownish'oil .is poured into 10 g. of aluminium oxide. Elution'with benzene-and evaporation to dryness of theeluates gives" the fi-[3-(5-benzyloxy) -indolyl]-ethyl carb'am'ic' acid is'o amyl ester as a'pale pellow glass whichidoesf not crystallise.) V V n i (h) The above isoamyl alcohol: solution containing this? isoamyl urethane istreated with hydrogen under con tinuous stirring at five atm. pressure momtemperemre; about 25 C.) in presence of 28 'g. of 10%" palladium oii" carbon catalyst until no more hydrogen isadso'rbed' (about five hours). The filtered isoamyl aloliol solutioncon tains B [3-(5-hydroxy)-indo1yl]eethyl'carbandic"acid isoamyl'esten; It is then evaporated to dryness' under re-i:

.in order to hydrolys'e the .carbamic.'ester. group The greenish solution, after'additionof;14.4 'g of'crystal lis ed? sodium acetate; is; neutralisedj tq coags red with; odiunr bicarbonate "are finesse east the sep'arate d' sadism ride.

propionic acidby a mixed melting point with authentic;

of new: 3

(i) 36 g. of picric acid are added to the filtrate and most of the alcohol is evaporated under reduced pressure. Water warmed to 65 C. added to a volume of about 550 cc. The warm solution is filtered with charcoal: by cooling S-hydroxy-tryptamine picrate separates off as red needles, m. pt. l85187 with dec.: after concentration of the mother liquors under reduced pressure a further amount of the same picrate is obtained. (A sample recrystallised from water melts at 195196 C. and a mixed melting point With a pure sample of S-hydroxytryptamine picrate gives no depression.)

Example 6 (a), (b) -benzyloxy-indole-2-carboxyl-3-B-propionic acid is prepared as described in the steps (a) and (b) of Example 1.

(c) 80 g. of this indole dicarboxylic acid are converted into 5-benzyloxy-indole-3-fi-propionic acid (64 g.) according the step (c) of Example 5.

(d) A solution of 64 g. of the above crude indolemonocarboxylic acid in 640 cc. of absolute ethanol containing 3% of dry hydrogen chloride is refluxed for two hours. After cooling the mixture is poured into a solution of 65 g. of sodium bicarbonate in 1300 cc. of water thus obtaining 65.5 g. of the crude ethyl-S-benzyloxyindole-3-B-propionate which after crystallisation from hexane melts at 62-63 C. and is in good agreement with the formula C H O N: N% calc. 4.33, N% found 4.48).

(e) A mixture of 65 g. of the above ethyl ester, 1750 cc. of ethanol and 93 cc. of hydrazine hydrate is refluxed for one hour. By treating the solution in the same way as described in the step (e) of Example 1 for the transformation of the corresponding methyl ester into the hydrazide, 60.5 g. of crude 5-benzyloxy-indole-3-fipropionhydrazide, m. pt. 133134 C., are obtained. (The mixed melting point with a pure sample gives no depression.)

(f) 60 g. of this hydrazide are converted into the azide using acetic acid and sodium nitrite according to the directions of Example 1 at step (f).

(g) The so obtained dried benzene solution (about 900 cc.), containing the 5-benzyloxy-indole-3-fi-propionazide, is added dropwise to 76 cc. of anhydrous benzyl alcohol warmed at 130 C. in an oil bath: continuous distillation of benzene occurs. The solution is warmed at 130 C. for 30 minutes more after complete distillation of benzene. 76 cc. of xylene are added and the resulting brown solution is evaporated to dryness under reduced pressure. The residual oil is dissolved in 80 cc. of benzene and poured into a column of 1000 g. of aluminium oxide.

After complete elution with benzene the eluted solution is concentrated under reduced pressure to about 90 cc.: addition of 15-20 cc. of hexane causes the crystallisation of 50.3 g. of B-[3-(5-benzyloxy)-indolyl]-ethyl carbamic acid benzyl ester, as white needles melting at 70-72 C. The mother liquors are again treated with aluminium oxide so obtaining a further crop of the same product. Total yield 60 g. (77% of the theoretical amount). (An analytical sample recrystallised from benzene-hexane melts at 7273 C. and the determination of nitrogen content is in good agreement with the formula C H O N N% calc. 7, N% found 6.81.)

(h) To a solution of 60 g. of the above benzylurethane in 6 l. of ethanol and 144 cc. of normal hydrochloric acid, 30 g. of 10% palladium or carbon catalyst 14 are added. The mixture is treated with hydrogen with continuous stirring at six atrn. pressure (room temperature: about 25 C.) until no more hydrogen is adsorbed.

(i) To the so-obtained ethanolic solution, filtered from the catalyst, containing the S-hydroxy-tryptamine hydrochloride, 34.5 g. of picric acid are added. Elimination of the ethanol under reduced pressure to a volume of 850 cc. causes the crystallisation of most of the 5- hydroxy-tryptamine picrate as red needles: 45.5 g., 111. pt. 185-186 C. By concentration of the mother liquors further crops of crystals are collected: the total yield amounted to 60 g. (about (A mixed melting point of a water recrystallised sample with pure 5- hydroxy-tryptamine picrate gives no depression.)

(I) The S-hydroxy-tryptamine may be separated from the alcoholic solution, after the palladium-hydrogen treatment, in the form of its double salt with creatinine (sulfate). The handling is as follows: to an ethanolic solutionobtained by treatment of 60 g. of benzylurethane with hydrogen in presence of 10% palladium on carbon catalyst according to the above directions-17 g. of creatinine and then cc. of 2 N sulfuric acid are added. The mixture is heated to boiling With stirring and then cooled to 0 C.; S-hydroxy-tryptamine creatinine sulfate separates off as a white crystalline precipitate. The prod not is filtered on a Biichner funnel, washed with ethanol and dried: yield 55.5 g.: m. pt. 210211 C. with dec. (A water recrystallised sample melts at 213-214 C. with dec. and not gives depression when mixedwith an authentic sample of 5-hydroxy-tryptamine-creatinine-sulfate.)

We have again experienced that, after the benzene solution of the 5-benzyloxy-indole-3-t3-propionazide (from .60 g. of hydrazide) has been reacted With benzyl alcohol and all the benzene distilled, the crude benzyl alcohol solution of the B [3-(5-benzyloxy) -indolyl] -ethyl carbamic acid benzyl ester, when diluted to 6 l. with ethanol containing144 cc. of N hydrochloric acid, may be directly submitted to palladium-hydrogen treatment in a perfectly analogous way. In this case all the benzyl alcohol present is transformed into toluene. After elimination of the catalyst from the hydrogenated solution, 5-hydroxy-tryptamine picrate, as well as S-hydroxy-tryptamine-creatininesulfate, is obtained in a similar high yield.

What we claim is:

1. 5-benzyloxy-indole-3-;3-propionazide.

2. 5-benzyloxy-indole-3-fi-propionhydrazide.

References Cited in the file of this patent UNITED STATES PATENTS 2,057,948 Herdickerhofi Oct. 20, 1936 2,416,258 Jenkins et al. Feb. 18, 1947 2,708,197 Specter May 10, 1955 2,814,625 Specter Nov. 26, 1957 OTHER REFERENCES Berg et al.: J. Bio. chemi., vol. 85 (1930), pp. 219-231.

Weygand: Organic Preparations, p. 467 (1945), Interscience Publishers, Inc., New York.

Hill and Kelly: Organic Chemistry, p. 288, The Blakiston Company, Philadelphia, May 1943.

Murphy: Journ. Am. Pharm. Assoc., vol. 30, pp. 83-85 (1943).

Manske et al.: lour. Chem. Soc. (London), pp. 240- 242 (1927). 7

Organic Preparations, Weygand, pp. 196-197 (1945), Interscience Publishers, N.Y. 

1. 5-BENZYLOXY-IBDOLE-3-B-PROPINOAZIDE. 